Electrostatic image developing toner

ABSTRACT

An electrostatic image developing toner, characterized by containing at least a resin, a coloring agent and a compound of the formula (1), ##STR1## wherein R 1  and R 2  are respectively independently a C 1  -C 18  alkyl group or an aralkyl group which may have a substituent, and X is a halogen ion, an aromatic sulfonic acid ion which may have a substituent or an aromatic carboxylic acid ion which may have a substituent.

TECHNICAL FIELD

The present invention relates to an electrophotographic toner containinga certain specific compound.

BACKGROUND ART

In an image-forming process by means of an electrophotographic system,an electrostatic latent image is formed on an inorganic photoconductivematerial such as selenium, a selenium alloy, cadmium sulfide oramorphous silicon, or on an organic photoconductive material employing acharge-generating material and a charge-transporting material, and thelatent image is developed by a toner, then transferred and fixed on apaper sheet or a plastic film to obtain a visible image.

The photoconductive material may be positively electrifiable ornegatively electrifiable depending upon its construction. When a printedportion is remained as an electrostatic latent image by exposure,development is conducted by means of an oppositely electrifiable toner.On the other hand, when a printed portion is destaticized for reversaldevelopment, development is conducted by means of an equallyelectrifiable toner. A toner is composed of a binder resin, a coloringagent and other additives. However, in order to impart desiredtribocharge properties (such as desired charge up speed, tribochargelevel and tribocharge level stability), stability with time andenvironmental stability, it is common to use a charge-control agent. Theproperties of the toner will be substantially affected by thischarge-control agent.

In a case where a negatively electrifiable photoconductive material isused for development with an oppositely electrifiable toner, or apositively electrifiable photoconductive material is used for reversedevelopment, a positively electrifiable toner is used. In such a case, apositively electrifiable charge-control agent is used.

Further, in a case of a color toner, it is necessary to use a colorlesscharge-control agent or a charge-control agent with a pale color whichdoes not affect the color of the toner. Such pale-colored or colorlesscharge-control agents may, for example, be quaternary ammonium chloridecompounds disclosed in e.g. Japanese Unexamined Patent Publications No.119364/1982, No. 9154/1983 and No. 98742/1983.

However, these charge-control agents have various drawbacks such that acharged amount is unstable depending on storing conditions andparticularly that a charged amount in a toner which is high at theinitial stage of preparation of a developer, is remarkably loweredspecially when a temperature and a moisture are high. Further,parahalophenyl carboxylic acid disclosed in Japanese Unexamined PatentPublication No. 186752/1983 has such a drawback that thermostability ispoor. Also, the above-mentioned charge-control agents have lowelectrifying effects or provide oppositely electrifiable toners, or someof them are poor in dispersibility or chemical stability. Thus, none ofthem has fully satisfactory properties as a charge-control agent.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a charge-controlagent which has a high stability as a colorless compound and a gooddispersibility to a binder resin and being free from a deteriorationduring the preparation of a toner and which is capable of presenting atoner which has a good tribocharge property and which is capable ofconstantly presenting an image of high image quality under variousenvironmental conditions.

The present inventors have found a colorless stable compound which hasexcellent dispersibility in a binder resin and which is capable ofimparting an excellent tribocharge property to a toner, and have finallyinvented an excellent toner by using this compound as a charge-controlagent.

Namely, the present invention provides an electrostatic image developingtoner, characterized by containing at least a resin, a coloring agentand a compound of the formula (1), ##STR2## wherein R₁ and R₂ arerespectively independently a C₁ -C₁₈ alkyl group or an aralkyl groupwhich may have a substituent, and X is a halogen ion, an aromaticsulfonic acid ion which may have a substituent or an aromatic carboxylicacid ion which may have a substituent.

In the compound of the formula (1) used as a charge-control agent in thepresent invention, when R₁ and R₂ are an aralkyl group which may have asubstituent, they are particularly preferably a benzyl group andexamples of a substituent include a C₁ -C₄ alkyl group or a halogenatom. When X is an aromatic sulfonic acid ion which may have asubstituent, it is particularly preferably a benzenesulfonic acid ion ora naphthalenesulfonic acid ion, and examples of a substituent for thebenzenesulfonic acid ion include a C₁ -C₁₄ alkyl group, an amino group,a halogen atom or the like, and examples of a substituent for thenaphthalenesulfonic acid ion include a hydroxyl group, an amino group orthe like. When X is an aromatic carboxylic acid ion which may have asubstituent, it is particularly preferably a benzenecarboxyl acid ion,and examples of a substituent include a hydroxyl group, a C₁ -C₄ alkylgroup, a nitro group, a carboxylic group or the like. In any case, thesame or different plural substituents may be present.

A quaternary ammonium halide of the formula (1) used in the presentinvention, can be obtained generally by reacting a o-xylene dihalide anda secondary amine in an alcohol solvent in the presence of a base at atemperature of 60 to 80° C. for 4 to 8 hours. The quaternary ammoniumhalide thus obtained is dissolved in water or a water-containingalcohol, to which an aqueous solution of an alkali metal salt ofcarboxylic acid or an alkali metal salt of sulfonic acid or an aqueoussolution of an alkali halide is then added, and the resultant mixture isreacted at a temperature of 60 to 80° C. for 4 to 8 hours to obtainvarious pairs of ion compounds.

The following compounds may be mentioned as specific examples of thecompound of the present invention useful as a charge-control agent.##STR3##

Basically, the toner of the present invention comprises a binder resin,a coloring agent and the compound of the formula (1). As a method forproducing the toner of the present invention, there may be mentioned amethod wherein a mixture of such starting materials are kneaded by aheat-mixing apparatus while the binder resin is melted, and the mixtureis then cooled, followed by rough pulverization, fine pulverization andclassification, a method wherein a mixture of such starting materials isdissolved in a solvent and then sprayed to form fine particles, followedby drying and classification, or a method wherein the coloring agent andthe compound of the formula (1) are dispersed in suspended monomerparticles, followed by polymerization. The toner of the presentinvention can be produced by any of the above methods.

The toner of the present invention contains a compound of the formula(1) preferably in an amount of from 0.5 to 5 parts by weight to 100parts by weight of a binder resin.

As the binder resin, a polystyrene, a styrene-methacrylate copolymer, astyrene-propylene copolymer, a styrene-butadiene copolymer, an acrylicresin, a styrene-maleic acid copolymer, an olefin resin, a polyester, anepoxy resin, a polyurethane resin, a polyvinyl butyral, etc., may beused alone or in combination as a mixture.

As the coloring agent, carbon black is commonly used for a black toner.For color toners, the following coloring agents are usually employed.Namely, as a yellow coloring agent, an azo-type organic pigment such asCI pigment yellow 1, CI pigment yellow 5, CI pigment yellow 12 or CIpigment yellow 17, an inorganic pigment such as yellow oshre, or anoil-soluble dye such as CI solvent yellow 2, CI solvent yellow 6, CIsolvent yellow 14 or CI solvent yellow 19, may be mentioned. As amagenta coloring agent, an azo pigment such as CI pigment red 57 or CIpigment red 57:1, a xanthene pigment such as CI pigment violet 1 or CIpigment red 81, a thioindigo pigment such as CI pigment red 87, CI vatred 1 or CI pigment violet 38, or an oil-soluble dye such as CI solventred 19, CI solvent red 49 or CI solvent red 52, may be mentioned. As acyan coloring agent, a triphenyl methane pigment such as CI pigment blue1, a phthalocyanine pigment such as CI pigment blue 15 or CI pigmentblue 17, or an oil-soluble dye such as CI solvent blue 25, CI solventblue 40 or CI solvent blue 70, may be mentioned.

Such a coloring agent is used usually in an amount of from 1 to 15 partsby weight, preferably from 3 to 10 parts by weight, per 100 parts byweight of the binder resin.

The toner may further contain various additives such as hydrophobicsilica, metal soap, a fluorine-type surfactant, dioctyl phthalate, wax,tin oxide and electrically conductive zinc oxide for the purposes ofprotecting the photoconductive material or carrier, improving theflowability of the toner, regulating the thermal properties, electricalproperties and physical properties, regulating the electricalresistance, regulating the softening point and improving the fixingproperty.

When the toner of the present invention is used for a two-componentdeveloping agent, there may be employed, as a carrier, fine glass beads,iron powder, ferrite powder or a binder-type carrier of resin particleshaving magnetic particles dispersed therein, or a resin coated carrierhaving its surface coated with a polyester resin, a fluorine resin, anacrylic resin or a silicone resin. Further, the toner of the presentinvention exhibits excellent performance when used as a one-componenttoner.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted by such specific Examples. In thefollowing Examples, "parts" means "parts by weight".

EXAMPLE 1

One part of Compound No. 1, 5 parts of carbon black and 94 parts of astyrene-ethylhexyl methacrylate copolymer (monomer ratio=7/3) werekneaded by a heat-mixing apparatus. After cooling, the mixture wasroughly pulverized by a hammer mill, then finely pulverized by a jetmill and classified to obtain a black toner of from 10 to 12 μm. Thistoner was mixed with an iron powder carrier at a weight ratio of 4:100,and the mixture was shaked, whereby the toner was positively charged,and the tribocharge was measured by a blow off powder charge measuringapparatus and found to be +25 μc/g. This toner was used to copy an imageby a modified commercially available copying machiner whereby copyimages with an excellent image quality were obtained not only at theinitial stage but also after copying 10,000 sheets.

EXAMPLE 2

One part of Compound No. 2, 5 parts of carbon black and 94 parts of astyrene-ethylhexyl methacrylate copolymer (monomer ratio=7/3) werekneaded by a heat-mixing apparatus. After cooling, the mixture wasroughly pulverized by a hammer mill, then finely pulverized by a jetmill and classified to obtain a black toner of from 10 to 12 μm. Thistoner was mixed with an iron powder carrier at a weight ratio of 4:100,and the mixture was shaked, whereby the toner was negatively charged,and the tribocharge measured by a blow off powder charge measuringapparatus was +23 μc/g. This toner was used to copy an image by amodified commercially available copying machine, whereby copy imageswith an excellent image quality were obtained not only at the initialstage but also after copying 10,000 sheets.

EXAMPLE 3

One part of Compound No. 3, 5 parts of Spilon Blue 2BNH as a copperphthalocyanine type oil-soluble dye (product of Hodogaya Chemical Co.,Ltd.) and 94 parts of a styrene-butyl methacrylate copolymer (monomerratio=8/2) were kneaded by a heat-mixing apparatus. After cooling, themixture was roughly pulverized by a hammer mill, then finely pulverizedby a jet mill and classified to obtain a blue toner of from 10 to 12 μm.This toner was mixed with an iron powder carrier at a weight ratio of4:100, and the mixture was shaked, whereby the toner was positivelycharged, and the tribocharge measured by a blow off powder chargemeasuring apparatus was +18 μc/g. This toner was used to copy an imageby a modified commercially available copying machine, whereby copyimages with an excellent image quality were obtained not only at theinitial stage but also after copying 10,000 sheets.

EXAMPLE 4

One part of Compound No. 4, 5 parts of carbon black and 94 parts of astyrene-ethylhexyl methacrylate copolymer (monomer ratio=7/3) werekneaded by a heat-mixing apparatus. After cooling, the mixture wasroughly pulverized by a hammer mill, then finely pulverized by a jetmill and classified to obtain a black toner of from 10 to 12 μm. Thistoner was mixed with a silicone resin coated carrier at a weight ratioof 4:100, and the mixture was shaked, whereby the toner was positivelycharged, and the tribocharge measured by a blow off powder chargemeasuring apparatus was +15 μc/g. This toner was used to copy an imageby a modified commercially available copying machine, whereby copyimages with an excellent image quality were obtained not only at theinitial stage but also after copying 10,000 sheets.

EXAMPLE 5

One part of Compound No. 1, 40 parts of magnetic iron powder and 59parts of a styrene-ethylhexyl methacrylate copolymer (monomer ratio=7/3)were kneaded by a heat-mixing apparatus. After cooling, the mixture wasroughly pulverized by a hammer mill, then finely pulverized by a jetmill and classified to obtain a black toner of from 10 to 12 μm. Thistoner was mixed with a ferrite carrier, and the mixture was shaked,whereby the toner was positively charged. This toner was used to copy animage by a modified commercially available copying machine forone-component toner, whereby copy images with an excellent image qualitywere obtained.

EXAMPLES 6 to 10

Experiments were conducted in the same manner as in Example 1 exceptthat the compounds as identified in Table 1 were used instead ofCompound No. 1 in Example 1, and the results are shown in Table 1.

                  TABLE 1    ______________________________________                Tribo-                charge of                         Image quality    Example Compound  the toner       After copying    No.     No.       (+μc/g) Initial                                      10,000 sheets    ______________________________________    6       Compound  21         Clear                                      Clear            No. 7    7       Compound  20         Clear                                      Clear            No. 10    8       Compound  12         Clear                                      Clear            No. 17    9       Compound  13         Clear                                      Clear            No. 18    10      Compound  10         Clear                                      Clear            No. 23    ______________________________________

INDUSTRIAL APPLICABILITY

The toner of the present invention is an excellent electrophotographictoner containing, as a positively electrifiable charge-control agent, acolorless compound containing no metal, having such a good compatibilitywith a resin as to be uniformly dispersed and also having excellentpositive electrifiability, electrification build up property, stabilitywith time and environmental stability.

We claim:
 1. An electrostatic image developing toner, characterized bycontaining at least a resin, a coloring agent and a compound of theformula (1), ##STR4## wherein R₁ and R₂ are respectively independently aC₁ -C₁₈ alkyl group or an aralkyl group which may have a substituent,and X is a halogen ion, an aromatic sulfonic acid ion which may have asubstituent or an aromatic carboxylic acid ion which may have asubstituent.
 2. The electrostatic image developing toner according toclaim 1, which comprises 100 parts by weight of a binder resin, from 1to 15 parts by weight of a coloring agent and from 0.5 to 5 parts byweight of a compound of the formula (1).
 3. The electrostatic imagedeveloping toner according to claim 1, wherein the compound of theformula (1) is one of the following compounds: ##STR5##